L.M. Chen

Tunnel-regenerated multiple-active-region light-emitting diodes with high efficiency

Tunnel-regenerated multiple-active-region (TRMAR) light-emitting diodes (LEDs) with high quantum efficiency and high brightness have been proposed and fabricated. We have proved experimentally that the efficiency of the electrical luminescence and the on-axis luminous intensity of such TRMAR LEDs scaled linearly approximately with the number of the active regions. The on-axis luminous intensity of such TRMAR LEDs with only 3 mum GaP current spreading layer have exceeded 5 cd at 20 mA dc operation under 15 degrees package. The high-quantum-efficiency and high-brightness LEDs under the low injection level were realized

Doping tuned rectifying properties in La2−xSrxCuO4/Nb:SrTiO3 heterojunctions

Here, we carried out a study on strontium doping effect on the rectifying properties of La2−xSrxCuO4 (LSCO)/NSTO heterojunctions. The intimate relationship between the change in electronic structure of LSCO and the variation of diffusion potential (Vd) of the junction supports opportunities for detecting Fermi level shift and superconducting gap evolution of LSCO upon hole doping. The results agree well to generally perceived viewpoints obtained by other methods. Even the suppression of Fermi level shift in the underdoped regime and weak-coupling d-wave BCS superconductivity behavior in the overdoped regime of LSCO are clearly exhibited by the tuned rectifying behaviors. This work not only reveals rich properties of LSCO/NSTO but also opens an alternative route to monitor the Fermi level and superconducting gap of high-temperature superconductors.

Fabrication of CdS∕Si nanocable heterostructures by one-step thermal evaporation

Coaxial CdS∕Si nanocable heterostructures with a length of hundreds of micrometers and an average diameter of 100nm were fabricated via one-step thermal evaporation of CdS powder under experimentally controlled conditions. The CdS cores have a hexagonal crystal structure. The Si sheaths are amorphous and can be directly grown on the CdS surfaces from the silicon substrate via a vapor-liquid-solid mechanism without an extra Si source. The photoluminescence of the nanocables presents two emission bands, around 510 and 590nm. This simple method may be applied to other Si-sheathed heterostructures, which can be used in nanodevices with various functions.

The study of novel high brightness 620 nm AlGaInP light emitting diodes

The problem of conventional light emitting diodes (LEDs) was analyzed. A novel tunnel-regenerated multiple-active-region light-emitting diode with high quantum efficiency and high brightness has been proposed and fabricated. We have proved theoretically that the efficiency of the electrical luminescence and the on-axis luminous intensity of such novel LEDs scaled linearly approximately with the number of the active regions. The on-axis luminous intensity of such novel LED with only 3 /spl mu/m GaP current spreading layer has exceeded 5cd at 20 mA DC operation under 15/spl deg/ package. The ultrahigh quantum efficiency and ultrahigh brightness LED under the low injection level was realized.